In a method of making a spunbond nonwoven from endless filaments made of a thermoplastic polymer, a spinneret spins the filaments and a cooler is provided for cooling the spun filaments. Between the spinneret and the cooler at least one monomer aspirator aspirates gases released during the spinning process.
Endless filaments with their quasi-continuous length differ from staple fibers that have shorter lengths of 10 to 60 mm, for example. With the monomer aspirator, air and/or gas is vacuumed out of the filament-forming space directly beneath the spinneret. This achieves the result that gases emerging in the form of monomers, oligomers, decomposition products and the like along with the polymer filaments can be removed at least partially from the filament-forming space and/or from the apparatus.
Basically, such an apparatus in various embodiments is known from practice. With these apparatuses, the filaments are spun by a spinneret, then cooled in a cooler and next passed through a stretcher and ultimately deposited on a support to form a spunbond nonwoven. Such an apparatus is also referred to as a spunbonding machine. Many of these known apparatuses have the disadvantage that the filaments often cannot be deposited to form a spunbond nonwoven in a satisfactory manner without defects. Irregularities in the form of flaws or defects in the spunbond nonwoven occur while the filament is being deposited. The homogeneity of a spunbond nonwoven is impaired to a more or less great extent due to these defects and/or disturbances. So-called drips that result from one or more filaments pulling away and forming accumulations of melt are one cause of defects in a spunbond nonwoven. These drips create flaws, i.e. thick spots, in the spunbond nonwoven and/or stick to the support for the spunbond nonwoven. Such drips and/or defects are usually larger than 2×2 mm. Defects in the spunbond nonwoven also result from so-called “hard pieces” that occur in that due to loss of tension, a spun filament can relax, recoil and in this way form a cluster that sticks together because of the molten condition of the filament. In doing so, there is usually no breakaway of the filament. The resulting defects in the spunbond nonwoven are usually less than 2×2 mm in size and but they are usually tangible and/or visible. The present invention is based on the discovery that such defects and/or flaws occur in a spunbond nonwoven in particular at higher filament speeds and/or at throughputs greater than 120 kg/h/m and in particular greater than 150 kg/h/m. Such irregularities in the spunbond nonwoven can also be observed at greater spinning zone depths in particular.
There have been efforts in the past to reduce the problems described above by treating the filaments more uniformly in the cooler and/or cooling them more uniformly with cooling air, for example, in order to achieve a more uniform filament flow and/or a more uniform filament treatment. These measures have led to only limited success, in particular at higher throughputs. Therefore, the apparatuses known in practice need to be improved.